Unit3單元高考閱讀閱讀提示：城市的興起壯大，城市的興起又衰落，這背后的原因是什么？本文以紐約和道森兩個城市為例，給出了隱藏在背后的真正推手。Citiesusuallyhaveagoodreasonforbeingwheretheyare,likeanearbyportorriver.Peoplesettleintheseplacesbecausetheyareeasytogettoandnaturallysuitedtocommunicationsandtrade.NewYorkCity,forexample,isnearalargeharbouratthemouthoftheHudsonRiver.Over300yearsitspopulationgrewgraduallyfrom800peopleto8million.Butnotallcitiesdevelopslowlyoveralongperiodoftime.Boomtownsgrowfromnothingalmostovernight.In1896,Dawson,Canada,wasunmappedwilderness(荒野).Butgoldwasdiscoveredtherein1897,andtwoyearslater,itwasoneofthelargestcitiesintheWest,withapopulationof30,000.DawsondidnothaveanyofthenaturalconveniencesofcitieslikeLondonorParis.Peoplewentthereforgold.Theytravelledoversnow-coveredmountainsandsailedhundredsofmilesupicyrivers.ThepathtoDawsonwascoveredwiththirtyfeetofwetsnowthatcouldfallwithoutwarning.Anavalanche(2iAi)onceclosedthepath,killing63people.FormanywhomadeittoDawson,however,therewardswereworththedifficulttrip.Ofthefirst20,000peoplewhodugforgold,4,000gotrich.About100ofthesestayedrichmenfortherestoftheirlives.Butnomatterhowrichtheywere.DawsonwasnevercomfortableNecessitieslikefoodandwoodwereveryexpensive.Butsoon,thegoldthatDawsondependedonhadallbeenfound.Thecitywascrowdedwithdisappointedpeoplewithnointerestinsettlingdown,andwhentheyheardtherewerenewgolddiscoveriesinAlaska,theyleftDawsonCityasquicklyastheyhadcome.Today,peoplestillcomeandgo-toseewheretheCanadiangoldrus